(1) Field of Invention
The present invention relates to the field of bathymetry, specifically technology for identifying a uniform distribution data set for producing bathymetric surface maps.
(2) Description of the Prior Art
Underwater navigation has been, and continues to be, problematic. Navigation technologies commonly used on land, such as Global Positioning Systems (GPS), are unreliable for underwater navigation. Electromagnetic wave dissipation in water renders technologies such as GPS useless. Without underwater beacons or long baseline navigation, vehicles operating underwater need to autonomously determine their position. Changes in vessel pitch caused by the acceleration of the vessel or other factors can alter the accuracy of bathymetric data substantially. It is necessary to develop and use detailed underwater maps for non-traditional navigation methods.
Known bathymetric software cannot accurately characterize continuously changing bathymetric data sets without complex, time consuming calculations. For example, the gridding method, a mapping system employed by current software programs known in the art for characterizing underwater terrain, defines grid node locations or a fixed number of points to use in a particular grid cell. Because the gridding method relies on a defined grid location or a fixed number of points, it is an unreliable method for mapping terrain which is constantly changing, skewing the accuracy of a resulting map. In addition, the calculations to determine more accurate data from the gridding method require time consuming processing of complex mathematical models, such as multiple regression analysis.
Autonomous underwater vehicles (AUVs) currently rely on the contours of bathymetric surface maps that often contain antiquated or inadequate data. Significant topographical information, known as georeferences, may not appear on those maps. Missed georeferences can cause navigational errors and interfere with AUV missions or even damage expensive AUVs.
For example, U.S. Pat. No. 5,012,675 teaches a system for integrating multiple mappable variables by determining grid node values and associating the grid node values with a map index to create a grid node suite. Cluster locations are used to assign earth features to create a map. U.S. Pat. No. 6,721,694 teaches a system using grid cell spacing for mapping the depths of seabed floors. However, neither system addresses the effects of outlier and anomaly data. Because these systems cannot adjust for such data, resulting bathymetric maps can contain multiple inaccuracies.
U.S. Pat. No. 7,337,069 teaches a system for measuring the thicknesses of sedimentary layers in a basin using existing topographical and seismic data and applying an iterative inversion procedure. While the iterative processes make this system more reliable for determining the thicknesses of underwater sedimentary sequences, this system is also not sufficiently accurate for creating reliable underwater maps for use by AUVs.
U.S. patent application Ser Nos. 11/654,015 now U.S. Pat. No. 8,060,254 and 12/311,050 now U.S. Pat. No. 8,295,554 teach methods for generating maps using RANSAC algorithms. However, both methods are designed for mapping above-water terrain, which is less changeable. Neither method is able to generate a reliable map of underwater terrain or capable of effectively filtering of outlier data.